>And what else does the backer get, apart from the product?
The whole point is to see the product come to market. A good project is expected to try and sweeten the deal somehow for backers who pledge more money. (Signed pieces, interviews with founder, etc etc.)
You get the thing you want, which you wouldn't get otherwise. It's also a way for people to put their money where their mouths are: instead of bullshitting and saying, "Yeah, I'd love X, I'd pay for X" on some forum, if you want X and someone has it on kickstarter, you can prove that you want it.
Plus, sometimes Kickstarted projects end up in all kinds of places; for example, I got a CustomSLR strap: http://www.customslr.com , which is exactly as good as I'd hoped, and the product / company was originally funded through Kickstarter.
The whole point is to see the product come to market. A good project is expected to try and sweeten the deal somehow for backers who pledge more money. (Signed pieces, interviews with founder, etc etc.)